The present invention relates to an implantable tubular device such as a stent to be implanted in human body such as a blood vessel, a bile duct, a trachea, an esophagus, an ureter, and internal organs to improve a stenotic lesion or a total occlusion formed in the lumens.
To cure various diseases that are caused when the blood vessel or lumens are stenosis or occlusion, the stent which is a tubular-shaped medical appliance is implanted at the stenotic lesion or the total occlusion to expand them and secure the lumen thereof.
The stent is classified into a self-expandable stent and a balloon expandable stent, depending on the function thereof and an implantation method. The balloon expandable stent itself has no dilating function. After the balloon expandable stent is inserted into a target lesion, a balloon expanded inside the stent in an extent almost equal to the normal diameter of the lumen of the target lesion is inflated to dilate (plastic deformation) the stent by the inflation force of the balloon so that the stent comes in close contact with the inner surface of the target lesion.
To deliver the stent to a desired portion of a human body, it is necessary that the mounted balloon and the stent are flexible. As a method of improving the flexibility of an approximately tubular stent having a plurality of annular units disposed axially and joining portions joining adjacent annular units to each other, the method of reducing the number of joining portions (articulation) disposed between the adjacent annular units is known(i.e. mono-link stent).
However, this method is incapable of improving the flexibility of the annular unit. Therefore, there is a demand for the development of an implantable device, such as a stent to be implanted in lumens, which is flexible so that it can pass smoothly through a curve portion of the human body.
The present invention has been made to solve the above-described problem. Therefore, it is an object of the present invention to provide an implantable tubular device, for example, a stent, having a deformable portion to improve the flexibility of an annular unit of the device so that the device can pass easily through a bent portion of a human body